Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): Martin Lemoine This paper argues in a first part that the observation of anisotropies at energies close to the GZK cut-off strongly argues in favor of the existence of protons at these energies. It then discusses the possible source of such protons, providing first general bounds on the luminosity of the source and on the amount of energy to be released in the ultra-high energy range. The necessary conditions point towards relativistic shock acceleration as an acceleration agent. Then, it discusses the physics of relativistic shock acceleration from a more microphysical point of view.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): Hyesung Kang Cosmological hydrodynamic simulations have demonstrated that shock waves could be produced in the intergalactic medium by supersonic flow motions during the course of hierarchical clustering of the large-scale-structure in the Universe. Similar to interplanetary shocks and supernova remnants (SNRs), these structure formation shocks can accelerate cosmic ray (CR) protons and electrons via diffusive shock acceleration. External accretion shocks, which form in the outermost surfaces of nonlinear structures, are as strong as SNR shocks and could be potential accelerations sites for high energy CR protons up to 1018 eV. But it could be difficult to detect their signatures due to extremely low kinetic energy flux associated with those accretion shocks. On the other hand, radiative features of internal shocks in the hot intracluster medium have been identified as temperature and density discontinuities in X-ray observations and diffuse radio emission from accelerated CR electrons. However, the non-detection of gamma-ray emission from galaxy clusters due to π0 decay still remains to be an outstanding problem.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): Daniele Fargion, Pietro Oliva Every Gamma Ray Burst (GRB) model where the progenitor is assumed to be a highly relativistic hadronic jet escaping from the interior of an exploding star whose electron-pair secondaries are feeding the jet's engine, necessarily (except for very fine-tuned cases) leads to a high average neutrino over photon radiant exposure (radiance) ratio well above unity, though the present observed average IceCube neutrino radiance is at most comparable to the gamma in the GRB one. Therefore no hadronic GRB, fireball or hadronic thin precessing jet, escaping exploding star in tunneled beam, can fit the actual observations. The absence of any high energy neutrino event correlated to GRB stand against such hadronic jetted models. A new model is shown here, based on a purely electronic progenitor jet, leading to electron pair jet, fed by neutrons stripped from a Neutron Star (NS) by tidal forces of a Black Hole (BH) or a NS companion, it may overcome these limitations. Such thin precessing spinning electron pair jets explain unsolved puzzles such as the existence of the X-ray precursor in many GRBs. Such a pure electron jet model, disentangling gamma from (absent) neutrinos, explains naturally why there is no gamma GRB correlates with any simultaneous TeV IceCube astrophysical neutrinos. A thin persistent electronic beaming, born in an empty compact binary system has the ability to offer the answer for a sudden engine (the thin jet) whose output may be comparable, off axis, to 1044–1047 erg s-1. The jet power is fed by a stripped neutron mass skin by tidal forces, feeding accretion disk. The consequent jet blazing to us on axis occurs within the inner jet cone beamed by a spiral charged disk at highest apparent output. In rare cases, the NS, while being stripped by the BH companion, will suddenly become unstable by the tidal disruption and it will explode and it will shine during the GRB afterglow, with an (apparent) late SN-like event birth. Primitive SN outer chemical mass shells, should be retro illuminated by such a NS explosion, re-brightening the relic nuclei as in a SN-like spectral line signature. To disentangle the common SN explosion from our proposal NS-SN event we suggest to follow the eventual radiative decay shining due to Cobalt and Nichel decay signature: it should be present in most SN, but it will be (almost) absent in suggested GRB with late NS-SN explosion.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): Anabella T. Araudo, Anthony R. Bell, Katherine M. Blundell We study the hotspots of powerful radiogalaxies, where electrons accelerated at the jet termination shock emit synchrotron radiation. The turnover of the synchrotron spectrum is typically observed between infrared and optical frequencies, indicating that the maximum energy of non-thermal electrons accelerated at the shock is ≲ TeV for a canonical magnetic field of ∼100 μG. We show that this maximum energy cannot be constrained by synchrotron losses as usually assumed, unless the jet density is unreasonably large and most of the jet upstream energy goes to non-thermal particles. We test this result by considering a sample of hotspots observed at radio, infrared and optical wavelengths.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): Sarka Wykes, Andrew M. Taylor, Justin D. Bray, Martin J. Hardcastle, Michael Hillas In the light of the recently predicted isotopic composition of the kpc-scale jet in Centaurus A, we re-investigate whether this source could be responsible for some of the ultra-high energy cosmic rays detected by the Pierre Auger Observatory. We find that a nearby source like Centaurus A is well motivated by the composition and spectral shape, and that such sources should start to dominate the flux above ∼ 4 EeV. The best-fitting isotopes from our modelling, with the maximum 56Fe energy fixed at 250 EeV, are of intermediate mass, 12C to 16O, while the best-fitting particle index is 2.3.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): Damiano Caprioli We suggest that ultra-high-energy (UHE) cosmic rays (CRs) may be accelerated in ultra-relativistic flows via a one-shot mechanism, the “espresso” acceleration, in which already-energetic particles are generally boosted by a factor of ∼Γ2 in energy, where Γ is the flow Lorentz factor. More precisely, we consider blazar-like ultra-relativistic jets propagating into a halo of “seed” CRs produced in supernova remnants, which can accelerate UHECRs up to 1020 eV. Such a re-acceleration process naturally accounts for the chemical composition measured by the Pierre Auger Collaboration, which resembles the one around and above the knee in the CR spectrum, and is consistent with the distribution of potential sources in the local universe; particularly intriguing is the coincidence of the powerful blazar Mrk 421 with the hotspot reported by the Telescope Array Collaboration.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): P. Picozza, P. Spillantini, L. Marcelli Direct research on cosmic rays in the energy region between tens MeV/n and few TeV/n has been extensively undertaken by experiments on board stratospheric balloons, satellites, Space Stations, since the sixties. The main goals are the search for primordial antimatter, dark matter annihilation signals and exotic particles and the study of the mechanisms of production, acceleration and propagation of cosmic rays. The monitoring of the cosmic ray solar modulation, the detection of solar flares and studies on the radiation belts around the Earth complete the research program. A review of the major results up to an energy of few TeV obtained by the previous and the current experiments, mainly PAMELA and AMS-02, will be presented in this article.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): A. Vacchi, LOFT collaboration The Large Observatory For x-ray Timing (LOFT) is a mission concept exploiting a novel detector solution and constitutes the base for a series of subsequent projects in various states of advancement. Thanks to the unprecedented combination of effective area and spectral resolution of its main instrument and the uniquely large field of view of its wide field monitor, LOFT will be able to study the behavior of matter in extreme conditions such as the strong gravitational field in the innermost regions close to black holes and neutron stars and the supra-nuclear densities in the interiors of neutron stars. The science payload is based on a Large Area Detector (LAD,>8m2 effective area, 2–30 keV, 240 eV spectral resolution, 1 degree collimated field of view) and a Wide Field Monitor (WFM, 2–50 keV, 4 steradian field of view, 1 arcmin source location accuracy, 300 eV spectral resolution). The WFM is equipped with an on-board system for bright events (e.g., GRB) localization. The trigger time and position of these events are broadcast to the ground within 30 s from discovery. In this paper we present the structure of the mission concept.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): A.M. Bykov, D.C. Ellison, P.E. Gladilin, S.M. Osipov New observations of high-energy cosmic rays (CRs), gamma-rays and neutrinos have caused an intense debate about their origin. Detection of the most powerful astrophysical neutrinos with E> 1015 eV by IceCube and detection of the light composition of the CR spectrum above the ‘knee’ made by LOFAR frame have intensified the debate over whether the sources are galactic or extragalactic. H.E.S.S. observations of very high-energy gamma-emission from compact galactic stellar clusters Westerlund 1 and Cl*1806-20 are also important for developing a model for a galactic PeVatron. We argue that expanding young supernova (SN) shells in compact stellar clusters can be very efficient PeV CR accelerators. The energy spectrum of protons in such an accelerator is hard with a broad spectral upturn above TeV before a break at multi-PeV energies, providing a large energy flux in the high-energy end of the spectrum. The acceleration stage in the colliding shock flow lasts for a few hundred years after the supernova explosion producing high-energy CRs that escape the accelerator and diffuse through the ambient matter producing gamma-rays and neutrinos in inelastic interacions with the ambient matter. Known supernova remnants interacting with stellar winds in the compact clusters of young massive stars Westerlund I and Cl*1806-20 can be associated with the sources of the TeV regime gamma-emission detected by H.E.S.S. and can be responsible for a fraction of the high-energy neutrinos detected with the IceCube observatory. We argue that these high-energy CR accelerators may also provide the light CR galactic component detected by LOFAR.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): Noemie Globus I examine the question of the origin of the Ultrahigh Energy Cosmic Rays (UHECRs) in the light of the data available at the highest energies.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): Piero Spillantini, Piero Mazzinghi, Paolo Sandri In last decade the technology for light mass, deployable and active mirrors for space applications reached a high Technological Readiness Level (TRL), and it is now ripe to be applied to an EUSO-like experiment for observing from space the particle showers produced by ultra-high energy charged CRs and neutrinos in the terrestrial atmosphere. The instrument should compromise between two conflicting requirements to the optical systems: (a) a wide as possible FoV for maximizing the volume of atmosphere observed from an Earth orbit in order to maximize the reachable energy of observed CRs; (b) a wide as possible pupil for maximizing the collected light for reaching down an enough low energy threshold for overlapping with the observations of ground based observatories. The high TRL reached in the realization of light mass, deployable active mirrors promises to improve the performance of the present EUSO project while reaching down an energy threshold of a few tens EeV. Therefore a new EUSO-like experiment should likely allows to observe some cosmogenic neutrino events, their number depending from the distribution and properties of the sources. Besides its main mission of observing ultra high energy CRs (UHECR), it can be considered a precursor or path-finder for addressing the problems to be afforded for the realization of an Observatory of ultra-high energy neutrinos, such as the realization of very large pupil and large FoV optical systems, the optimization of their number in a possible neutrino observatory, and the analysis machinery for identifying the neutrino events in the flood of the charged CR generated events.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): A.W. Strong Some common ideas which are often taken as known or self-evident are put in question: the detection (or not) of the gamma-ray ‘pion bump’, the importance of CR diffusive reacceleration, and the energy range of extragalactic cosmic rays.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): Aya Bamba X-ray observations are one of the strong tools to study acceleration sites of cosmic rays, not only with synchrotron emission but also with thermal emission from heated plasma. Thermal X-rays with emission lines give us plenty of information on temperature, density, plasma time scale and so on, for heated interstellar medium and ejecta of progenitors, which are critical to understand the background plasma of the acceleration sites. It is debated for long time about which environment strongly accelerate particles, thin environment with faster shocks or thick environment with amplified magnetic field. It is also important tp known in which environment and when accelerated particles can escape to be cosmic rays, which is totally open issue to be solved. Observations of low energy cosmic rays in the MeV range is also crucial to understand the injection of accelerated particles. In this paper, we will show recent results with X-ray observations, as hints of environments of acceleration and escape sites on shocks of supernova remnants.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): Alberto Carramiñana, HAWC Collaboration The HAWC γ-ray observatory is adding a fresh view of the high-energy sky through the unbiased survey of two thirds of the celestial sphere. HAWC has found TeV emission from 39 sources, a third of which were not previously detected. Most of the HAWC sources are in the Milky Way, either towards the Galactic anti-center or along the First Galactic Quadrant which features a Δℓ≃80∘ band of TeV emission spanning from Cygnus down to the vicinity of the Galactic Center. These cosmic accelerators are presented in a comparative context with other ground-based and space-borne high energy observatories.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): Andrea Vittino, Carmelo Evoli, Daniele Gaggero, Giuseppe Di Bernardo, Mattia Di Mauro, Arianna Ligorini, Piero Ullio, Dario Grasso We introduce DRAGON2, the new version of the public software package designed to study cosmic-ray propagation in the Galaxy. Our aim is to illustrate the approach followed in the writing of the code and to present its most important features. We describe the properties of the numerical scheme that has been adopted in DRAGON2 to implement the different processes related to cosmic-ray transport and we investigate its correctness by comparing our numerical results with a set of analytical solutions. Starting from these validation tests, we study in detail the performances of the code by probing the different factors that influence its accuracy and its speed under a wide range of different conditions. Lastly, we investigate the new features introduced in DRAGON2 in the treatment of diffusion, energy losses and reacceleration and their impact on the predicted fluxes, in comparison also with the results given by the previous version of the code.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): Elena Orlando, Gudlaugur Johannesson, Igor V. Moskalenko, Troy A. Porter, Andrew Strong Information on cosmic-ray (CR) composition comes from direct CR measurements while their distribution in the Galaxy is evaluated from observations of their associated diffuse emission in the range from radio to gamma rays. Even though the main interaction processes are identified, more and more precise observations provide an opportunity to study more subtle effects and pose a challenge to the propagation models.GALPROP is a sophisticated CR propagation code that is being developed for about 20 years. It provides a unified framework for interpretations of data from many different types of experiments. It is used for a description of direct CR measurements and associated interstellar emissions (radio to gamma rays), thereby providing important information about CR injection and propagation in the interstellar medium. By accounting for all relevant observables at a time, the GALPROP code brings together theoretical predictions, interpretation of the most recent observations, and helps to reveal the signatures of new phenomena.In this paper we review latest applications of GALPROP and address ongoing and near future improvements. We are discussing effects of different propagation models, and of the transition from cylindrically symmetrical models to a proper 3D description of the components of the interstellar medium and the source distribution.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): Gwenael Giacinti, John G. Kirk We study the role of local interstellar turbulence in shaping the large-scale anisotropy in the arrival directions of TeV–PeV cosmic-rays (CRs) on the sky. Assuming pitch-angle diffusion of CRs in a magnetic flux tube containing the Earth, we compute the CR anisotropy for Goldreich-Sridhar turbulence, and for isotropic fast modes. The narrow deficits in the 400 TeV and 2 PeV data sets of IceTop can be fitted for some parameters of the turbulence. The data also rule out a part of the parameter space. The shape of the CR anisotropy may be used as a local probe of the still poorly known properties of the interstellar turbulence and of CR transport.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): P. Blasi The description of the transport of cosmic rays in magnetized media is central to both acceleration and propagation of these particles in our Galaxy and outside. The investigation of the process of particle acceleration, especially at shock waves, has already emphasized that non-linear effects such as self-generation of waves and dynamical reaction of cosmic rays on the background plasmas, are crucial if to achieve a physical understanding of the origin of cosmic rays. Here we discuss how similar non-linear effects on Galactic scales may affect the propagation of cosmic rays, not only through the excitation of plasma waves important for particle scattering, but also by inducing the motion of the interstellar medium in the direction opposite to the gravitational pull exerted by matter in the Galaxy, thereby resulting in the launching of a wind. The recent discovery of several unexpected features in cosmic ray spectra (discrepant hardening, spectral breaks in the H and He spectra, rising positron fraction and unexpectedly hard antiproton spectrum) raises the question of whether at least some of these effects may be attributed to poorly understood aspects of cosmic ray transport.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): Yves A. Gallant Pulsars, and more precisely their wind nebulae, are perhaps the most likely astrophysical sources of high-energy cosmic-ray electrons and especially positrons, and in particular of the excess positronic component above ∼20 GeV measured by PAMELA, Fermi-LAT and AMS-02. While e± pairs are created in pulsar magnetospheres, their acceleration to relevant cosmic-ray energies likely occurs at the pulsar wind termination shock, and they are subsequently confined in the pulsar wind nebula (PWN) until late stages of its evolution. We discuss the implications of radiative and adiabatic energy losses for the likely contributions of different stages of PWN evolution to the observed cosmic-ray e± spectrum, and highlight the plausibly dominant contribution of late, subsonic expansion and especially bow-shock PWN phases.The most recently opened observational window on PWNe, with implications for accelerated e± in the relevant energy range, is the domain of TeV γ-rays. I review the properties of the population of PWNe revealed in this energy domain, in particular by the H.E.S.S. array of Cherenkov telescopes and its Galactic Plane Survey, and discuss the constraints which these place on the evolution of middle-aged PWNe. Finally, I briefly review the possibility of hadron acceleration in PWNe, and discuss theoretical and observational constraints which limit a plausible major contribution of these objects to the bulk of the (hadronic) Galactic cosmic-ray spectrum.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): Laila Vleeschower Calas, Sarah Kaufmann, César Álvarez Ochoa, Omar Tibolla We present the results from the data analysis of the XMM-Newton observation (53.6 ks) on PSR J1849-0001. We studied in detail the X-ray emission of this pulsar and we found extended emission (up to ≈ 100 arcsec) from the Pulsar Wind Nebula (PWN), confirming that this is a case of a Pulsar/PWN system and strengthening the evidence that X-ray, hard X-ray and TeV gamma-ray sources are manifestations of the same system. Another important result of our study is the clear evidence that the X-ray PWN of PSR J1849-0001 is asymmetric.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): Patrizia A. Caraveo According to standard theoretical interpretations, in neutron stars' magnetospheres particles are accelerated along the magnetic field lines where the highly-magnetized surrounding offers the ideal conditions to make them radiate high-energy gamma-rays (E ≥ 100 MeV) that bear the timing signature of their parent neutron star. Moreover, the accelerated particles (mostly electrons and positrons) can either move outward, to propagate into space, or be funnelled back, towards the star surface. While particles impinging on the neutron star surface generate hot spots, detectable in X-rays, outgoing ones could light-up the neutron star surroundings giving rise to extended features, visible both in X-and in Very-High-Energy (VHE) gamma-rays (E ≥ 100 GeV).By combining gamma-ray light curves and spectra with the X-ray emission, both thermal (from the hot spots) and non thermal (from somewhere in the magnetosphere) we can try to map the emission geography within the light cylinder. Moreover, we can trace the particles' propagation outside the neutron stars' magnetospheres through their synchrotron emission, responsible for X-ray extended features, and their VHE gamma-rays inverse Compton emission, which give rise to extended sources, whose shapes, however, appear different from that of the corresponding X-ray ones since they are produced by particles of different energies.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): S. Kaufmann, O. Tibolla A large part of the Galactic sources emitting very high energy (VHE;> 1011 eV) gamma-rays are currently still unidentified. The evolution of Pulsar Wind Nebulae (PWNe) plays a crucial role in interpreting these sources. The time-dependent modeling of PWNe has been tested on a sample of well-known young and intermediate age PWNe; and it is currently applied to the full-sample of unidentified VHE Galactic sources. The consequences of this interpretation go far beyond the interpretation of “dark sources” (i.e. VHE gamma-ray sources without lower energies, radio or X-ray, counterparts): e.g. there could be strong implication in the origin of cosmic rays and (when considering a leptonic origin of the gamma-ray signal) they can be important for reinterpreting the detection of starburst galaxies in the TeV gamma-ray band. Moreover, the number of Galactic VHE sources is currently increasing with further observation by Imaging Atmospheric Cherenkov Telescopes (IACTs) and by the advent of more sensitive water Cherenkov telescopes such as HAWC (High-Altitude Water Cherenkov Observatory); therefore the physical interpretation of unidentified sources becomes more and more crucial.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): Benoît Cerutti Pulsar magnetospheres are efficient particle accelerators, as evidenced by high-energy gamma-ray observations. Where and how particle acceleration occurs are difficult questions to answer because it results from a complex interplay between relativistic electrodynamics, pair creation and non-thermal radiation. The recent development of global particle-in-cell simulations allows, for the first time, to address this problem from first principles and self-consistently. Simulations indicate that relativistic reconnection in the equatorial current sheet plays a key role in particle acceleration and the emission of high-energy radiation. We discuss these results in the context of young gamma-ray pulsars.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): D.O. Chernyshov, P. Caselli, K.S. Cheng, V.A. Dogiel, A.V. Ivlev, C.M. Ko We analyze interaction of fast charged particles with Galactic molecular clouds. As a results of energy losses inside the clouds, a particle flux, converging to the cloud, is formed in the cloud vicinity. This flux, in its turn, excites there an MHD-turbulence by the streaming instability, which scatter the primary particles. Therefore the CR/cloud interaction is a complex problem described by a system of non-linear equations. We suggested a model of CR penetration into the dense cloud interior through their diffuse outer envelope. Three different regimes of CR propagation are realized in the envelope depending of CR energy: 1) Low energy particles with energies of tens of MeV are almost frozen into the MHD waves and propagate by convection with Alfven velocity. These particle do not reach the dense interior because of energy losses; 2) High energy particles with energies above ten GeV do not experience any scattering and propagate freely with luminal velocities. 3) In the intermediate energy range a ”mirroring shield” is formed between the diffuse envelope and the dense interior which prevents free CR penetration into the interior from outside. This effect is a function of the hydrogen density in the diffuse envelope and the spectrum of CRs in the intracloud medium.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): V.A. Dogiel, K.S. Cheng, D.O. Chernyshov, A.D. Erlykin, C.-M. Ko, A.W. Wolfendale We give a short review of processes of stochastic acceleration in the Galaxy. We discuss: how to estimate correctly the number of accelerated particles, and at which condition the stochastic mechanism is able to generate power-law nonthermal spectra. We present an analysis of stochastic acceleration in the Galactic halo and discuss whether this mechanism can be responsible for production of high energy electrons there, which emit gamma-ray and microwave emission from the giant Fermi bubbles. Lastly, we discuss whether the effects of stochastic acceleration can explain the CR distribution in the Galactic disk (CR gradient).

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): David Eichler Evidence is reviewed that shock-accelerated cosmic rays (CRs) are typically produced in sufficient quantity as to modify the flow into the shock and thereby regulate the acceleration of lower energy particles.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): Vladimir Zeković, Bojan Arbutina A collisionless shock wave is treated as a streaming plasma instability in the interstellar medium (ISM). We assume that in a steady state, this instability propagates through the ISM as a self-driven plasma instability, whereby the parameters of the instability are determined such that it causes density and velocity jumps as well as isotropization of the particle velocities, which then must be in accordance with MHD theory. The process of resonant interaction and particle scattering off such instability and their backscattering to an upstream region is simulated. We find that some ISM particles bounce off a shock and thus become suprathermal and eligible to enter the process of acceleration to cosmic ray energies by the mechanism of diffuse shock acceleration.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): M.Z. Pavlović, D. Urošević, B. Arbutina Supernova remnants (SNRs) are believed to accelerate particles up to high energies, at least reaching a few PeV, through the mechanism of diffusive shock acceleration (DSA). Detection of synchrotron radio emission from cosmic ray (CR) electrons supports this picture. We give preliminary results for the global radio emission evolution for SNRs, based on two-dimensional hydrodynamic simulations of SNRs evolving through a homogeneous ambient medium, coupled with particle acceleration and magnetic field amplification (MFA). We coupled a simple Blasi's semi-analytical model that deals with these non-linear effects in a quantitative way and changes hydrodynamics by means of an effective adiabatic index. We obtained the radio flux density increasing with time in the free expansion phase, achieving its peak value slightly before the beginning of the Sedov phase, and then decreasing during later phases.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): Giovanni Morlino Recent results obtained by analyzing diffuse γ-ray emission detected by Fermi-LAT show a substantial variation of the CR spectrum as a function of the distance from the Galactic Center. For energies up to tens of GeV, the CR proton density in the outer Galaxy appears to be weakly dependent upon the galactocentric distance while the density in the central region of the Galaxy was found to exceed the value measured in the outer Galaxy. At the same time, Fermi-LAT data suggest a gradual spectral softening while moving outward from the center of the Galaxy to its outskirts. These findings represent a challenge for standard calculations of CR propagation based on assuming a uniform diffusion coefficient within the Galactic volume. Here we present a model of non-linear CR propagation in which transport is due to particle scattering and advection off self-generated turbulence. We will show that for a realistic distribution of CR sources following the spatial distribution of supernova remnants and the space dependence of the magnetic field on galactocentric distance, both the spatial profile of CR density and the spectral softening can easily be accounted for.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): L. Di Venere, F. de Palma, -LAT collaboration Supernova Remnants (SNRs) are a very well studied class of objects in our Galaxy and are closely related to the origin of Cosmic Rays (CRs), being candidates to host the acceleration process of Galactic CRs. Accelerated particles in SNRs can produce γ-rays through interactions with gas (nucleon-nucleon interactions or e± bremsstrahlung) or low-energy photons (inverse Compton scattering by electrons). In more than eight years of data taking, the Large Area Telescope (LAT) onboard the Fermi satellite, has detected more than 30 SNRs in the γ-ray energy band. The energy range in which Fermi-LAT is sensitive, namely from less than 100 MeV up to a few hundred GeV, is crucial to provide information on the physical processes occurring at the source and disentangle between lepton-based and hadron-based interpretation models. The Fermi-LAT collaboration has recently performed a systematic study of the known SNRs, producing the first Supernova Remnant Catalog in the GeV energy range. The spatial and spectral information obtained allow a systematic study of the SNR characteristics, which, together with multi-wavelength information, provide more general constraints on the CR population of our Galaxy. We present here the latest results from the observations of Galactic SNRs by Fermi-LAT, with a particular focus on the recent results obtained in the first SNR catalog.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): M.A. Malkov Recent observations of galactic cosmic rays (CR) in the 1-500 GeV energy range have revealed striking deviations from what deemed “standard.” The anomalies cut across hadronic and leptonic CRs. I discuss findings that challenge physical mechanisms long held responsible for the CR production in galactic supernova remnants (SNR). I also consider some new physics of particle acceleration in SNR shocks that is not part of conventional models but may explain the anomalies. However, a possible 20–30% excess remains unaccounted for in the e+/e+ ratio over the range of a few 100 GeV. If not explained by future models, it suggests an additional source of positrons such as a dark matter decay/annihilation or pulsar contribution. Earlier efforts to explain both the e+/e− and p/He anomalies with the “standard” models by adjusting the SNR environmental parameters and multiple sources are critically assessed.

Abstract: Publication date: April–June 2018Source: Nuclear and Particle Physics Proceedings, Volumes 297–299Author(s): Luke O'C. Drury The motivations for reconsidering the origin(s) of cosmic rays remain as valid as they were two years ago. While we have a standard model, or better perhaps a standard folklore, the reasons to be somewhat sceptical have if anything increased. In this talk I will survey the arguments for and against the standard SNR origin for the Galactic component of the cosmic rays. I will also briefly review the evidence for a distinct component coming from the Galactic centre.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): S. Honda, ATLAS collaboration After the discovery of the Higgs boson, the measurement of its coupling properties are of particular importance. In this talk measurement of the cross sections and couplings of the Higgs boson in bosonic and fermionic decay channels with the ATLAS detector are presented.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): Eugenio Megías, Mariano Quirós, Lindber Salas We study the recently found anomalies in B-meson decays within a scenario with a warped extra dimension where the Standard Model (SM) fermions are propagating in the bulk. The anomalies are then interpreted as the result of the exchange of heavy vector resonances with electroweak (EW) quantum numbers. The model naturally leads to lepton-flavor universality (LFU) violation when different flavor fermions are differently localized along the extra dimension, signaling a different degree of compositeness in the dual holographic theory.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): G. Vasseur, BABAR Collaboration The BABAR Collaboration pursues an intensive program studying hadronic cross sections in low-energy electron-positron annihilations, accessible via initial-state radiation. Our measurements allow significant improvements in the precision of the predicted value of the muon anomalous magnetic moment. These improvements are necessary for shedding light on the current 3 σ difference between the predicted and the experimental values. We have published results on a number of processes with from two to six hadrons in the final state and other final states are currently under investigation. We report here on the most recent results obtained by analysing the entire BABAR dataset. We present in particular the measurement of the mode with two charged pions and two neutral pions and the measurement of the full set of final states with two kaons and one or two pions.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): Martin Ripka, BESIII collaboration A difference of more than three standard deviations between is currently observed between the direct experimental measurement and the Standard Model prediction of the anomalous magnetic moment of the muon (g−2)μ. The hadronic vacuum polarization contributions can be related to hadronic cross sections using the optical theorem. Precision measurements of the hadronic cross sections e+e−→π+π−, π+π−π0, π+π−2π0, ωπ0 and π+π−3π0 are performed at the BESIII experiment located in Beijing, China. The initial state radiation method is used to access the energy regions of interest for (g−2)μ. Our results will improve the precision of the Standard Model prediction of (g−2)μ.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): Yuping Guo, BESIII Collaboration The anomalous magnetic momentum of muon, aμ, has been measured in experiment and calculated in theory with a precision up to ∼0.5 ppm. But there is a long standing 3 to 4 standard deviations between these two accurate values. The dominant contribution to the uncertainty in the theoretical calculation comes from the hadroninc contribution, including contributions from the hadronic vacuum polarization and the hadronic light-by-light. The meson transition form factors measured in two photon process at BESIII can be used as input or constrain for the calculation of the hadronic light-by-light contribution to aμ. Recent experimental activities, including the measurements of the transition form factor of π0, η, and η′, and the cross section of γγ⁎→π+π− are presented.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): O.V. Teryaev, V.I. Zakharov We consider the problem of transferring overall rotation of quark-gluon plasma to polarization of hyperons along the rotation axis. As a toy theoretical model, we exploit that of pionic superfluidity induced by chemical potentials violating isotopic symmetry. Apparently, the model accounts only for the light degrees of freedom, that is pions. The rotation, however, results in vortices which are infinitely thin in the hydrodynamic approximation. Field theory resolves the singularity and predicts that the core of the vortices is build up on spins of baryons. We review consequences from the quark-hadron duality in this case. First, an anomalous triangle graph in effective field theory turns to be dual to the vorticity term in the standard hydrodynamic expansion. And, then, the overall coefficient determining the polarization of baryons is fixed by duality with the triangle graph in the fundamental field theory.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): J.P. Carlomagno, M. Loewe We compare two order parameters for the deconfinement transition, induced by thermal and density effects, commonly used in the literature, namely the thermal and density evolution of the continuum threshold s0, within the frame of the QCD sum rules, and the trace of the Polyakov loop Φ in the framework of a nonlocal S U(2) chiral quark model. We include in our discussion the evolution of the chiral quark condensate, the parameter that characterizes the chiral symmetry restoration. We found that essentially both order parameters, s0 and Φ, provide the same information for the deconfinement transition, both for the zero and finite chemical potential cases. At zero density, the critical temperatures in both cases coincide exactly and, in the case of finite baryonic chemical potential μ, we find evidence for the appearance of a quarkyonic phase.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): César Ayala We consider a phenomenologycal parametrization of the QCD running coupling which arises from the dispersion relation respecting the holomorphic properties of the physical QCD observables in the complex momentum plane. The parameters are fixed by the following requirements: 1) at enough high energies, it reproduces the underlying perturbative coupling, 2) at intermediate energy momenta, it reproduces the experimental semihadronic tau decay ratio, and 3) in the deep IR regime, it satisfies the qualitative properties coming from recent lattice results. Finally, we apply this new coupling to low-energy available experimental data. In particular, to Borel sum rules for τ-decay, extracting the values of the dimension 4 and 6 condensates, to the V-channel Adler function, and to polarized Bjorken Sum Rule.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): Marco Frasca We solve exactly the Dyson-Schwinger equations for Yang-Mills theory in 3 and 4 dimensions. This permits us to obtain the exact correlation functions till order 2. In this way, the spectrum of the theory is straightforwardly obtained and comparison with lattice data can be accomplished. The results are in exceedingly good agreement with an error well below 1%. This extends both to 3 and 4 dimensions and varying the degree of the gauge group. These results provide a strong support to the value of the lattice computations and show once again how precise can be theoretical computations in quantum field theory.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): Huan-Huan Liu, BESIII Collaboration The BESIII has collected 1.3 billion J/ψ and 478 million ψ(3686) data since 2009. In this talk, we will introduce five recent analyses on light hadron spectroscopy at BESIII, including two studies on the X(1835), two partial wave analyses that are related to searching and studying glueball candidates, and one study on χc1.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): Bin-Long Wang Using 567 pb-1 of e+e− annihilation data collected at a center-of-mass energy of s = 4.6 GeV with the BESIII detector, four analyses of Λc+ decay are reported in the QCD 17 conference. The measurements of singly Cabibbo-suppressed decays Λc+→pπ+π− and pK+K− are performed, and the relative branching fractions with respect to the Cabibbo-favored decay Λc+→pK−π+ are given, the absolute branching fractions are also obtained for these two decays. Evidence for the singly Cabibbo-suppressed decay Λc+→pη is found with 4.2σ, and the upper limit for Λc+→pπ0is reported. The absolute branching fraction B(Λc+→Σ−π+π+π0) is determined to be (2.11±0.33±0.14)%. In addition, an improved measurement of B(Λc+→Σ−π+π+) is determined as (1.81 ± 0.17 ± 0.09)%. The branching fraction of the inclusive decay Λc+→Λ+X is measured to be B(Λc+→Λ+X)=(38.2−2.2+2.8±0.6)%.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): Joan Soto We report on a recent investigation on heavy quarkonium hybrids that goes beyond the usual Born-Oppenheimer approximation by including not only the mixing between nearby hybrid states but also the mixing with quarkonium states. We use a systematic effective field theory framework based on NRQCD together with lattice QCD inputs. Short and long distance constraints from weak coupling pNRQCD and the QCD effective string theory are also employed. We calculate the quarkonium and hybrid spectrum for charmonium and bottomonium, and estimate a number of decay widths. Most of the isospin zero XYZ resonances fit in our spectrum either as quarkonia or as hybrid states. The mixing of hybrid states with quarkonia produces enhanced spin symmetry violations, which are instrumental to understand certain decays. We also present new results on the hyperfine splittings.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): A. Palameta, J. Ho, D. Harnett, T.G. Steele We use QCD Laplace sum-rules to explore mixing between conventional mesons and hybrids in the heavy quarkonium vector JPC=1−− channel. Our cross-correlator includes perturbation theory and contributions proportional to the four-dimensional and six-dimensional gluon condensates. We input experimentally determined charmonium and bottomonium hadron masses into both single and multi-resonance models in order to test them for conventional meson and hybrid components. In the charmonium sector we find evidence for meson-hybrid mixing in the J/ψ and a ≈ 4.3 GeV resonance. In the bottomonium sector, we find that the ϒ(1S), ϒ(2S), ϒ(3S), and ϒ(4S) all exhibit mixing.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): H. Dag, A. Turkan In this work, we studied the radial excitations of X(4140) and like states within QCD sum rules. We chose three molecular and three diquark-antidiquark currents with the quark content cc‾ss‾ and JPC = 0++, 1++, 2++, and estimated the masses and the meson coupling constants of the first excited states coupling to these currents in the framework of QCD sum rules. The ground states coupling to these currents were analyzed in a previous work and we have shown that all of these ground states have degenerate masses within 10 MeV neighborhood of exotic meson X(4140). For the excited states, the masses are not found to be degenerate. We found that scalar and tensor currents are coupling to Ds⁎D‾s⁎ threshold. However for the axial vector currents, the first excited states found to have mass compatible with X(4274), which was measured in the same decay with X(4140). Thus we conclude that X(4274) could be a radial excitation of X(4140).

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): Bin Wang, BESIII Collaboration The BESIII experiment has collected about 6 fb-1 luminosity data samples above 3.8 GeV. Recent result on the charmonium(-like) states (or called XYZ states) from BESIII experiment is presented in this talk, including the production and decay of the X(3872) states, the vector Y states, as well as the charged and neutral charmoniumlike Zc states.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): S. Bethke The strong coupling constant αs(MZ) is determined using inclusive top-quark pair production cross section measurements performed at the LHC and at the Tevatron. Individual values of αs(MZ) are extracted from measurements of different experiments at several centre-of-mass energies, using QCD predictions complete in NNLO perturbation theory, supplemented with NNLL approximations to all orders, and suitable sets of parton distribution functions. These values are then combined using a likelyhood-based approach, with special emphasis on a consistent treatment of systemtic uncertainties and their correlations. The final combined result is αs(MZ)=0.1177−0.0036+0.0034.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): Matteo Negrini, ATLAS Collaboration Highlights on recent measurements of top quark properties in ATLAS, using pp collision data at s = 8 TeV and 13 TeV, are presented. The measurements of the top quark polarization and spin correlation coefficients, the W boson helicity fractions, the structure of the Wtb vertex, the associated production of a tt‾ pair with a vector boson or a photon, and the top quark mass are all in agreement with the Standard Model expectations.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): A.D. Morton, CMS Collaboration Results of several single top physics measurements that the CMS Collaboration has produced in proton-proton collisions at the LHC at centre-of-mass energies of 7, 8 and 13 TeV, are presented. Separate investigations of the inclusive, fiducial, and differential cross section measurements in the t-channel, the production of top via the s-channel, and the measurements of standard model parameters and rare processes involving a top quark are discussed.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): L. Massa, ATLAS collaboration Measurements of the inclusive and differential cross-sections for top-quark pair and single top production cross sections in proton-proton collisions with the ATLAS detector at the Large Hadron Collider are presented at centre-of-mass energies of 8 TeV and 13 TeV.The inclusive measurements reach high precision and are compared to the best available theoretical calculations. These measurements, including results using boosted tops, probe our understanding of top-pair production in the TeV regime. The results are compared to Monte Carlo generators implementing LO and NLO matrix elements matched with parton showers and NLO QCD calculations.For the t-channel single top measurement, the single top-quark and anti-top-quark total production cross-sections, their ratio, as well as differential cross sections are also presented. A measurement of the production cross section of a single top quark in association with a W boson, the second largest single-top production mode, is also presented. Finally, measurements of the properties of the Wtb vertex allow to set limits on anomalous couplings. All measurements are compared to state-of-the-art theoretical calculations.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): Andrew Foster, ATLAS Collaboration Recent results in the soft QCD sector of the Standard Model are presented. Measurements of low energy observables were performed with the ATLAS detector at the Large Hadron Collider at CERN. In particular, underlying event, charged particle correlation and diffraction observables are reported and various models of Monte Carlo predictions are compared to the data.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): Julien Hamon, ALICE Collaboration In this paper, an overview of recent D0, D+ and D*+ measurements, performed by ALICE in proton–proton collisions at s = 2.76, 5, 7, 8 and 13 TeV, is reported. The minimum-bias production cross sections, as well as their energy and species dependences, are compared to perturbative QCD calculations. The evolution of the D-meson yields with the event multiplicity is compared to phenomenological models.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): A. Mirjalili, A. Jamali, M. Khellat, M. Akrami We discuss the possibility of obtaining mass and scale dependent kernels for the DGLAP evolution equations within the momentum space subtraction (MOM) class of renormalization schemes. Such well-behaved kernels would be necessary to evolve quark densities from zero at an initial scale to higher energy scales. However, in the light-front formulation of quark density operators, we are first required to carefully extract the renormalization procedures and develop a consistent definition of renormalization factors for the MOM scheme. As a result, we are led to some conditions for the implementation of MOM class of schemes for the quark densities in the context of parton model.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): Günter Grindhammer, H1 and ZEUS Collaborations Recent results on the combination of open charm and beauty production data in deep-inelastic scattering and their mparison to perturbative QCD calculations at next-to-leading order and approximate next-to-next-to-leading order are presented. The combined data are used to extract the masses of the charm and beauty quarks at next-to-leading order. Inclusive jet and dijet cross sections in deep-inelastic scattering are used to extract the strong coupling αs(mZ) at next-to-next-to-leading order for the first time. Finally, further new observables measured for the description of prompt photons plus jet production in deep-inelastic scattering and their comparison to perturbative QCD calculations are shown.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): Andrii Verbytskyi We study jet production in e+e− annihilation to hadrons with data recorded by the OPAL experiment at LEP at centre-of-mass energies between 91 GeV and 209 GeV. The jet production rates were measured with Durham and for the first time with the anti-kt and SISCone jet clustering algorithms. We compare the data with predictions by modern Monte Carlo event generators.

Abstract: Publication date: January–March 2018Source: Nuclear and Particle Physics Proceedings, Volumes 294–296Author(s): Sebastien Prince, ATLAS Collaboration The production of prompt isolated photons at hadron colliders provides a stringent test of perturbative QCD and can be used to probe the proton structure. The production of prompt photons in association with jets provides an additional testing ground for perturbative QCD with a hard colourless probe less affected by hadronisation effects than jet production. At the LHC, the ATLAS collaboration has performed precise measurements of the inclusive production of isolated prompt photons at a centre-of-mass energy of 13 TeV. The dynamics of isolated-photon plus jet production in pp collisions at a centre-of-mass energy of 8 TeV have also been measured. In addition, the integrated and differential cross sections for isolated photon pairs at a centre-of-mass energy of 8 TeV have been measured. The results are compared with state-of-the art theory predictions at next-to-leading order in perturbative QCD.